Biological monitoring of cellular effects of omalizumab with basophil degranulation test (BAT) in severe asthma

The use of anti-IgE antibodies (Omalizumab) for the treatment of severe asthma is the first approach with biological drugs in this setting. IgE bound to receptor on responsive cells induce both mast cell and basophil degranulation with release of new mediators responsible of clinical features. There aren't objective tests to dimonstrate the biological effects to this treatment. We evaluated basophil degranulation during treatment with Omalizumab using a basophil degranulation test based on a one-step method of basophil staining after exposure to a specific allergen with flow citometry that shows basophilic reactivity in vitro and their degranulation after contact with specific allergens. This method is based on recognition of peripheric blood cells positive to marking with monoclonal antibody CD123 that together with citophluorimetric caratheristic by Forward and Side Scatter and the contemporary negativity of expression of superficial antigen HLA-DR,identify basophil granocyte subset. In these cells after specific stimulation in vitro, is possible to identify IgE degranulation for the expression on the citoplasmatic surface of the antigen with monoclonal antibody CD63. Seven patients were examined with the test baseline and after 12 and 24 months of OMA treatment. After 24 months of treatment degranulated basophil cells were 0.7% in comparison 53.9%at 12 months and 53.5% at baseline and this decrease was associated both to clinical improvements and reduction in oral corticosteroid daily dosage.Basophil degranulation test may be an appropriate method to evaluate Omalizumab biologic therapy in severe asthma where response and treatment duration are important aims.